Signaling system



May 12, 1931I H. P. cLAUsEN 1,804,675

SIGNALING SYSTEM Filed March 2, 1927 55./ Y ...o-...IIE

l WIL...Y

f fie. 2,4

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common transmitting station.

Patented May 12, 1931 HENEYP. oLAUsEN, or MAMeEoNEoi-z, NEW Yoan. assioiron 'ro BELL TELEPHONE v p LABona'roieiEs, iNcoEronA'rEn, or NEW YORK.' N. Y., A conronn'rioiv 0E NEW YORK SIGNALING SYSTEM vApplication filed March 2, 1927. Serial No. 171,971. i

, This invention relates to Wave communication, and particularly to'signal receiving systems. Specifically stated, an object of the inventioii is to conserve the energy of energysupply means employedto energize electric space discharge devices'of signal receiving systems. f A preferred embodiment of the invention comprises a vacuum `tube radio receiving system having means for placing the system I in operativel or stand-by condition for short periods at given relatively Widely separated times, to enable a transmitting station to signal the receiving1 station during any desired ones of vsuch periods. rl`he timed production of the stand-by condition is accomplished by a clock-controlled switch which closes tliefilainent heating circuit `of the receiver only duringthe periods which are to be stand-by periods. Thus, the energy of the filament current and plate current supply sources' is conserved.V The conservation' is especially important When dry cells are employed to supply filament heating current. Upon receiving a calledsignal, the operator at the receiving s-tatioiiactuates means to ymaintain the filament heating circuit `of the radio receiver operative during the transmission of the message about to be 'sent to him..

The invention also contemplates an extension of the feature ]ust described .to a pluralityof receiving stations controlled from a network is especially adapted. for municipal or police service. l

vThe radio receiverjmaygbe connected by Wire to a plurality of outlyinor receiving stations each provided with means selectively operable from the transmitting station to call the operator at the particular receiving station.

Fig. l is a circuit diagram. of one einlbodiment of the invention; Fig. 2 is a' circuit diagram of an embodiment of theV invention involving selective calling of receiving stations; and Fig. 2A is a circuit diagram of a transmitting stati'onffor use in connection With the circuit of Fig. 2.

Such a radio coil 2 and a variable tuning condenser 3.

Coil 2 is coupled to an inductance coil 4 of a tunino circuit 5 in the input circuit of a three electrode electric space discharge detector tube 6. A jack 7 is connected across lthe plate and iilainent` of the detector. A telephone receiver 8 is adapted to be plugged into the jack, so that the receiver 8 Will be connected in the output circuit of the detector tube.

Space` current from a section of a platel current battery 10 is supplied to tube 6 through the primary Winding of an. audio frequency` transformer ll. A condenser l2 connected across the Winding bypasses cur- 'rentof radio frequency, around the Winding. `The secondary Winding of the transformer isuconnected across the grid and filament of an electric kspace discharge amplifier tube i5.

ySpace current from battery 10 is supplied to tubel through the Winding or" an alteriiating current'relay 16. kAcross the relayvyvinding is connecteda condenser 17, foriny ing ,with the Winding a circuit tuned to a'ffrequency of, for example, 2000 cycles per second. W'lien the relay is energized its contact closes a lcircuit from a k battery 20 througha signal,` as for example, an alarm or call bell 2l. I s i e .Y Heating current from battery 20 is supplied to the tubek filaments in parallel, through acloclrVL controlled switch 25`vvhich lcloses the filament circuit periodically. For example, the switch may close the filament circuitfor one minute at intervals ofon'e half hour. l

`A- switch 26-is so associated with jack 7 as to be in closed condition When the receiver 8 is plugged in the jack, and to be open when theplug connectedtothe receiveris outv of thejacln The switch 26 is connected in parallel with switch 25. i Y The antenna l and the circuit 5 aremaintained-tuned to the carrier frequency eniployed by the radio transmitting station' k(not shown) from which the receiving system is to receive communications. When a message is to be sent to the receiving sta tion, a call signal is first transmitted, for causing operation of bell 21, in order to indicate at the receiving system that a message is about to be transmitted. This call signal may be sent by modulating the carrier frequency with a wave Vof the frequency to which condenser 17 and the winding of re'- lay 16 are tuned. The call signal is sent at one of the times when switch 25 is in closed condition. This moduiated wave is detected by tube 6 and the modulating wave is amplified by tube 15 and causes relay 16 to close the circuit of the call bell. Thereupon the attendant or operator at the receiving station inseits the plug connected to receiver 8 in ack 7, yin( readiness to receive the message about to be transmitted. At the eX- piration of the period during which switch 25 should remain closed, the transmitting station discontinues the n'iodiilationV of the carrier wavel by the wave for sending the call signal, and transmits the desired speech or other message by modulating wave with a wave corresponding to the message. This modulated .vave` is detected by tube 6 and the message is received in the receiver 8. The filament lieating'circuit of the tubes is maintained closed by switch 26 until, at the termination of the n essage, the operatorat the `receiving station withdraws the plug from jack 7. Even though the fre quency to which condenser 17 and the winding of relay 16 are tuned be a frequency in the voice frequencyrange, the voice current Vcomponent which has this frequency will not, upon reaching the relay, `be of sufiicient magnitude to operate the relay. There the messages to be received are voice waves, the frequency to which condenser 17 and relay 16 aretuned isy preferably a frequency at which the energy of the voice waves is small relative to the voice energy at other fre quencies.

Since the standby periods or periods during which the switch 25 is closed'may be small compared to the intervals between such periods, the drain on the batteries 20 and 10 overk a long period of time may be made small, and yet messages may be re` ceived without undue delay. rlhis is a matter of importance especially in cases in which Vthe use of dry cells for heating the tube filaments is desirable. Y

Y The transmitting station (not shown) may be a broadcasting station, as for example, a station operated by a-imunicipality, and radio receivers such as that described above may be installed at various locations, as indicated by the antennee 1a, 1b, 10, and 167.

. These receivers may all have their switches 25 closed simultaneously; or if desired, one or ,more stations, such as that associated with the antenna 1, may have the switch or Vswitches 25 closed, say for one minute each the Vcarrier antennae 1c and 1d, have their contacts such as 25 close, say for one minute each half hour, 20 minutes after the closing of the contacts such as 25 of the station with antenna 1. Still other groups may be employed.

The call signals for the stations represented by antennae 1, 1a, 1b, 1c, and 1d may all be operated by the same calling frequency; or, if desired, different receiving stations or different groups of receiving stations may have their condensers 17 and relay windings 16 tuned to different frequencies, so that when at any given time a given frequency is employed as the carrier modulating calling frequency at the transmitting station, the call bells of only those receiving static-iis which then have their switches such as 25 closed, and which moreover respond to the given calling frequency, will be operated.

Fig. 2 shows a radio receiver including an antenna 1 and a detector and an amplifier such as described above. However, the receiver in Fig. 2 is adapted to transfer the calling signals and messages which it receives to a line 28. The line extends to receiving stations 31, 32, 33 etc., which may be atconsiderable distances from each other and from the radio receiver. The stations are all alike, so only station 33 will be described. It includes an alarm or call signal,-as` for example call bell 21. Current for operating the bell is supplied by a battery 34 through a movable contact 35 of a selector or selectively operated circuit closer 40. The selector comprises an operating or stepping magnet 41 connected across line 28 in series with a condenser 42. The selector is of the type disclosed in U. S. patent to J. C. Field, No. 1,343,256, June 15, 1920. Current impulses flowing alternately in opposite directions through the magnet 41, or in other words, reversals of the current in magnet 41, cause the magnet to drive mecha- 'nisin (not shown) which steps the movable vidual tothe particular selector as distinguished'from the selectors at other stations. The combination of impulses may be created `in a manner indicated hereinafter by way of example. In response to its individual code or combination of impulses, the selector magnet causes the movable contact to close the circuit of bell 21 and maintains it closed for a desirable ringing period, atthe eX- piration` of which a releasing impulse is transmitted tofmagnet 41 over line 28. The releasing impulse may be transmitted to the magnet in a manner indicated hereinafter by way of example. In response to the releasing impulse, the magnet causes the movable contact to be returned to its normal position by a restoring spring (not shown).`

IStation 33 includes a telephone receiver `for receiving speech messages, for example, transmitted tothe station over line 28. The receiver normally rests on a receiver hook r46, thereby maintaining three receiver hoolry switches open. Y- The upper switch, when closed, connects the receiver across line 28, in series with a condenser 50. lhe two lowery switches when closed, conneet the two sides lof line 28 to ground through the two equal resistances 51, respectively. Y Y

At the radio receiver a voice frequenc transformer has itsr primary winding connected inthe output circuit of tube 6, in parallel with .the primary winding of transformer 11. The twobaclr contacts of a pulsing relay normally connect the two sides of line 28 to the two ends respectively, of the secondary winding of transformer 55.

f Whenever receiver 45 is off its hook, a

relay 62 is energized to maintain the filament heating'circuit of the tubes 6 and 15 closed. 'The circuit for thus energizing relay 62 is a simplex circuit extending from ground, through battery 10, conductorf, winding of relay 62, conductor 61, the two halves of the secondary winding of transformer 55, the two sides of line'28, the two lower switches of receiver hook 46, andthe two resistances 51 to earth. The contacts of the relay 62 are connected in parallel with the contacts of switch 25 and in parallel with the contacts of switch 26, so the lilament heating'circuit will be closed whenever the relay' or either of these switches is closed.

rlhe primary call signal relay 16 is operated by trains or groups of call signaling waves, which may be produced and transmitted to the relay winding as described hereinafter by way `of example. The wave trains or groups so transmitted to relay. 16 are sent to the vrelay ingiven combinations or codes. rlhe combinations correspond, vrespectively, to the above'mentioned combinations ofimpulses lof which each combination is individual to one of the selectors.

llllicnever the pulsing relay 60 is energized, due to closure ofthe contact of the primary call signal relay 16, the .relay 60 closes a circuit for sending a-current pulse over line 28 to each of the receiving stations 'J such as31, 82l and 33. This pulse `passes through the .magnets suchas l41 and charges the`condensers,such as 42. The circuit for this pulse extends from ground through bat,- tery=l0, conductor 63, conductor 64, outer front contactr of relay60, right hand conductor of line 28, in parallel through-the circuits comprisingv magnets 41 in series with condensers 42 at .the various receiving st-ations, through the left hand side of line 28, and inner front contact of relayGO, to

ground.- M t As indicated above, the selectors are:l designed tol steptheirmovable contacts inresponse to reversals of ycurrent through the selector magnet windings. By means of in magnet 41,v fromthe unidirectional current pulses sent overline 28 by closures of relay60. vEach closurecauses a pulse of current which traverses the magnet in Va given direction andv charges .the condenser. When the relay opens its front contacts and closes yits back lcontacts',the condenser discharges, sending current inthe reverse direction through the magnet 41, over a circuit extending from the-condenser through the magnet, right hand conductor of line 28, outer back contact of relay 60, secondary winding of transformer 55 in parallel with any impedance such' as impedance 7() with teryk 10, produces sufficient operating current for magnet 41. c

lFig. 2A shows,- by way ofeXample,fa radio transmitting station for sending call signalling waves and message waves to be received by the radioreceiver connected to the antenna 1 inFig. 2. In Fig. 2A., the contactsof a relay 87'V and the'back contacts of a relay 86 normally connect ya telephone transmitter 7 5 to the input circuitY of a voice frequency ampliier 6. `The amplifier-'may be of any suitable type, as forexample, an electric space discharge tube amplifier of condenser 42 thesey reversals are obtained,

Sies

usual type. The output side of the amplifier K is connected to aradio transmitter 77.. `The output side ofthis radio transmitter is connected witha transmitting antenna/8O.'` The radio transmitter may be of usual type, with a source ofradio frequency carrier current and means for modulating `this carrier current by voice currents fromvtransmitter v and amplifierG` when messages are to be sent, or by call signaling waves which are Etno delivered to amplifier/7 6 from a source of electro-motive force when the frontcontacts of'relay 86 and thecontacts of relay 87 are closed. The frequency of source 85 rico Fig.Y 2jare tuned. 'An impulse transmitter 89 is employed Vmay be, for example 2000 cycles per sec-ond,

or the frequency to which condenser 17 and the Winding of relay 16 in Fig. 2 aretuned. The carrier frequency is the frequency to which .the antenna 1l and the circuit 5 of for disconnecting the transmitter -7 5 from amplifier 76 and causing the carrier wave transmitted from the, radio transmitter to be modulated by a given combination (or codei) of trains' (or groups) of 2000-cycle lalternat-ions, this combination corresponddotted extensions of these lines, also associate other impulse transmitters with this battery and these relays in the same manner as in the case of the impulse transmitter 89. These other impulse transmitters are like the impulse transmitter 89, but are respectively adjusted to cause trainsvlor groups) of the 2000 cycle alternations from source'85 to be impressed on amplifier 76 in codes (or combinations) corresponding respectively to theimpulse combinations or codes individual to the selectors at the respective receiving Vstations (3,1, V32, etc.) other than station 33. Thus, there is at the transmitting station of Fig. 2A an impulse transmitter individual to each of the. receiving stations of Fig. 2, operable for causing operation ofthe call signal bell at the particular receiving station.

Normally the telephone transmitter V75 is connected to the amplifier 76 andthe source 85 isA disconnected from the amplifier.

lWhen relay86 is energized by operation of an `impulse transmitter as described. hereinafter, it disconnects the telephone transmitter Yfrom the amplifier, and connectsthe sourceV 85 tothe amplifier provided relay 87 'isnoteenergized Energizations of relay 87 while relay 86 is energized are caused by operation of the impulse transmitter as described hereinafter, to create properiytimed interruptions of the application of the 2000 cycle wave to the amplifier, the Vtiming of the interruptions being such that the resulting combination of 2000 cycle wave trains transmitted to the amplifier, corresponds to the impulse combination or code individual vto the receiving station for selection of which fthe impulse transmitter is designed. Impulse transmitter 89 comprises a rotatable disc 71 provided with teeth, certain Voperates spring 96.

ones of which may be blocked out by adjustable cams 94 and 95 to obtain the particular number and combination of effective teeth desired for calling a particular station. The disc is adapted to rotate in a counter-clockwise direction, for causing its teeth to control contact springs 96 and 97 in circuit with the relay 87. The free end of the contact spring 97 is bent downward, and carries an insulating roller 98 which, as the disc rotates, is adapted to ride on top of the cam 95 and separate ccntacts96 and 97 during the time of the passage of cam 95.

'The Contact spring 96 is normally out of engagement with the rotatable disc. During the revolution of the disc, spring 96 is in engagement with the disc, maintaining the circuit of the relay 86 closed to disconnect the telephone transmitter from the `amplifier 7 6, and to connect the source 85 to the amplifier during such times as the relay 87 is not energized. i

Assuming that while the clock controlled contact 25 is closed, the disc of transmitter 89 is caused to rotate for sending a call signal to step selector 40 toits circuit closing or bell ringing position. As the disc starts to rotate it causes springs to complete the vcircuit of relay 865 The relay disconnects Vthe telephone transmitter from amplifier 7 6 y and connects source 85 to the amplifier through the closed contacts of relay 87. Therefore the carrier wave from the radio transmitter is modulated by a 2000 cycle wave. The radio receiver detects this modulated wave,rto operate relay 16 by the result-ing 2000 cycle wave. Relay 16 operates relays 60 and 62, over a circuit extending from battery 10 through conductor 63, winding of relay 62, conductor 61, winding of relay 60, and contact of relay 16, to ground. Relay Y62 closes its contact, to shunt switch 25. Relay 62 is preferably made a slow release relay, for the purpose of avoiding opening of the filament circuit of tubes 6 and 15, should the switch 25 open before transmission of the selective code signal has been completed. Relay 60 applies potential from' battery 10 to line 28, charging condenserel2. `The charging pulse energizes magnet 41,7but the magnet releases its armature (not shown), and a restorin spring (not shown) restores contact 35 to the normal position of the contact, before the first tooth of the disc As explained in the bove mentioned Patent 1,343,256, the construction of the selector is such that, when the 'armature of magnet 41 returns to its normal (neutral) position, a holding pawl (not shown) is withdrawn from a position in which it prevents the restoring spring for the'movable Contact 35 from rotating the contact backward Ytoward the normal position of the contact; and if the holding pawl remains withdrawn from its holding posi- 'CII tion for a.sufiicientintervahthe restoring spring for the movable contact. returns the ,y contact to the normal position of the contact."

of the circuit of the winding of ielayl`87 atV springs 96 andl 97, with consequent interruptions of the application of the 2000cycle modulating wave to the amplifier 76. Each group or train ofimodulating waves applied to the radio transmitter causes the relay 16 to operate rela 60 with consequent application'of kthe vo tage of battery` 10 toline 28. The voltage thus applied tothe line causes a charging current for. condenser 42 to flow in one direction through the winding 41; and when the wave train ceases and relays 16'and 60 become deenergized, the condenser 42'discharges, sending current in the opposite direction through the winding 41. 4The reversals of current thus produced in wind-v ing 41 by the passage of the first group of teeth underspringf 96, cause the selector 40 to step'k its movablecontact 35 around, and an additional reversal and consequent additional step'of rotation of contact 35 occurs as the spring 96 rises from the space between two teeth to the cam surface of cam 94. Thev contact 35 is thus stepped around af distance corresponding to the total number of reversals in this group of reversalsthus produced by the first group of teeth and the cani 94.y The duration of the period in which spring 96 rests on cam 94 is sufficient to allow the restoring springs of the selectors to return'tlie .movable contacts ofthe selectors-,to their normal positions, but, as eX- plained in theV above mentioned Patent 1,343,256, those selectors, including the one at station 33, which are arranged to-respond to codes of reversals, the first group of which is Ymade up of the number of reversals in the group of reversals produced by the first group of teeth on disc 71 and the cam 94, will, iny releasing their armatures, cause a holding spring (not shown) towengage the movable contact and hold it in advanced position.l Y c As camV 94 passes from under spring 96 .and the second groupk of teeth pass under .the spring, a second set of trains (or groups) of modulating waves is applied to amplifier 76.*Consequentlyfa second set of energizations ofrelays 16 and g60 ensues. "Contact 35 is therefore stepped to a position in which it is held while cam 95 passes under roller 98 l I n y p vAs the third group zof teethand the initial portion of a smooth surface'100 of disc 71 pass under spring 96, a thirdsetof trains or groups of modulating wavesis. applied to amplifier 76,y and cause energizations of relaysv 16 and v60. Contact 35 is therefore stepped to its circuit closing position, where it is held during the period in which surface 100 is in mechanical and electricalv contact with spring 96. This period is a ringing period for the call bell 21. `The 2000 cycle modulating wave is not transmitted to amplifier 76 during this period.

After the ringing period, a smooth surface 101 of disc "1 passes under spring 96, causing the 2000 cycle modulating Wave to be transmitted to the amplifier, so that relays 16 and 60 operate and contact 35 is released,

and'is returned to its normal positionby its restoringspring (not shown).`

Vhen disc 71 reaches itsnormal position,

relay 86 is deenergized, and disconnects source 85 from the amplifier and connects the telephone transmitter 7 5 to the amplifier.

During the ringing period `or as vsoon thereafter as possible, the operator at station 33 removes receiver 45 fromiits hook, to connect the receiver 'to line 28 for listening to the message which is about to be transmitted from transmitter 75.

As explained above, while the receiveris off of'its hook the slow release relay 62 is energizedovei' the above traced simplex circuit, to maintain the filament heat-ing circuit for tubes 6 and 15 ciosed. VVhen the receiver is replaced, after transmission of the message has been completed, these circuitsr are .opened The condenser 50, if employed, kprevents Vany tendency for direct current to flow to receiver 45.

As indicated by the antenna 1'@ in Fig. 2,

a plurality of Asystems such as that shown in .i

tem of code signals individual to the receiving station. What is claimed is:

radio telephone receiving apparatus comprising a space discharge device, a local sourceof power therefor, timing means for i normally disassociating and forperiodically associatingfor short periods said device and said source of power, a circuitcontrolling device 'controlled by said space kdischarge device and vcontrollable through said device from' a distant radiotransniitting station,

whereby said transmitting station may operate said circuit vcontrollii'ig device during said periodsl and means operable by a local operator for associating said device and 4source of power independently of said timing means whereby said receiving apparatus may be maintained energized for longer periods when desired.

2. kA radio signaling network comprising a central station, a plurality of outlying stations, receiving apparatus at each of said outlying stations comprising a power operated device and a local source of power therefor, timing means for normally dis-V associating and for periodically associating.

said device and said source of power for short periods independently of said central station, a calling device for each of said outlying stations controllable from saidV central station only when said-source of power is associated with -said power operated device, whereby said central station may call each of said outlying stations during said periods, and means at each of said outlying stations operable by a local operator during any of said periods for associating said source with said power operated device independently of said timing means to enable said central station to communicate with saidoperatpr for a longer period.

3. A system comprising receiving circuits for receiving signals from a common source,

timing means for periodicallyV renderingv certain of said circuits operative to receive signals from said source for given time intervals, and timing means for periodically rendering certain of said circuits operative to receive signals from said source at times exclusive of said intervals.

4. In combination, a plurality ofY separated signal stations, call signal devices at said stations, respectively, station selectors at said stations, respectively, responsive to selecting impulses to select said stations in accordance with an impulse code and operate the call device at the selected station, common radio receiving means for saidv stations, for receiving radio waves representing signals and station selecting impulses, connecting means connecting said radio receiving means to said stations, and timing means for periodically rendering said radio receiving means operative.v s Y '5. In combination, a plurality of separated signal stations, call signal devices at said stations, respectively, station selectors at said stations, respectively, responsive to selecting impulses to select said stations in accordance with an impulse code and oper- `ate the call device at the selectedstation, a radio receiver common to certain of said stations `for receiving radio waves representing signals and station selecting impulses, another radio receiver-cominon to certain others of said stations, for receivingV radio waves representing signals and station selecting impulses, timing means for periodically rendering one ot said radio receiving circuits operative for given Vtime intervals, and timing means for periodica ly rendering said other radio receiver operative at times exclusive of said intervals.

6. A wave receiving system comprising selectors, means responsive to energy pulses for operating said selectors, timing means for periodically rendering said` first means operative, k'and meansresponsive to the operation of said first means by said pulses for maintaining said irst means operative between said pulses.

Y 7. In combination, a plurality of separated signal stations, message receiving means at said stations respectively, call signals at said stations, stationselectors at said stations respectively,responsive to selecting impulses to select said stations in accordance with an impulse code and operate the ca ll signal at the selected station, common radio receiving means for said stations, for receiving radio waves representing messages and station selecting impulses, connecting means connecting said radio receiving means to said stations,rmeans at each of said signal stations for connecting the message receiving means at the station .to said connecting means, timing means for periodically rendering'said radio receiving means'operative, and means responsive'to connection of any one of said message receiving means to said connecting means for maintaining said radio receiving means operative While said message receiving means is so connected.

8. In' combination, a signaling line, a plurality of signal stations connected to said line at separated points along the line, message receiving means at said stations respectively, calling. signals at said stations respectively, station selectors at said stations.

respectively, responsive to selecting impulses to select said stations in accordance with an impulse code and' operate the call signal at the selected station, radio receiving means connected tosaid line for receivin'g'radio waves representing signals and station selecting'impulses, means at each of said stations for connecting the message receivingV means at the station to said line, timing means for periodically rendering said radio receiving means operative, maintaining means Jfor maintaining said radio receiving means operative while said message receiving means is connected to said line, a simplex operating circuit for said maintaining means, said simplex circuit including said line, and means operable in response to connection of lsaid message receiving means to said line to close said simplex operating circuit.V

9. A'radio telephone system comprising a transmitting station and one "or more receiving stations, receiving apparatus at each of saidreceiving stations comprising, a power operated device, a source ofpower therefor,

.timing means Vfor normally dissociating and for periodicallyV associating-said device and source of power is associated with said power operated device whereby said transmitting station Vmy call anyone of said reios ceiving stations during such periods, and means operable at each receiving station for receiving messages from said transmitting station, said means maintaining said power operated device and said source of power associated independently of said timing means. n In Witness whereof, hereunto subscribe my name this 26thV day of February A. D.

HENRY P. CLAUSEN. 

